When a patient experiences a medical emergency, trained medical personnel may be summoned to provide emergency care. The medical personnel evaluate the condition of the patient and provide emergency treatment to restore a life sustaining condition and attempt to stabilize the patient.
When the patient has abruptly lost consciousness, the medical personnel check the patient's ECG and check for other vital signs such as the patient's pulse to determine whether the heart is perfusing, i.e., whether the heart is effectively pumping blood in a manner that will sustain the vital organs. The heart's stroke volume and rate are among the factors, which determine whether perfusion is adequate. Medical conditions such as ventricular fibrillation (VF), Ventricular Tachycardia (VT), or organized rhythms such as pulseless electrical activity (PEA) might be responsible for a failure of perfusion, which in turn might be responsible for the loss of consciousness. When the heart is not perfusing, the time required to determine and deliver the appropriate treatment is of great importance to the patient's chance of survival. The patient could die or suffer serious brain injury due to lack of oxygen unless perfusion is established promptly. Accordingly, it is important for the medical personnel to assess the condition of the patient promptly and take action that would benefit the patient.
Medical personnel typically bring an external defibrillator to the site of the emergency. The defibrillator may employ two or more electrodes to record an electrocardiogram (ECG). In addition, the defibrillator may prompt an operator, i.e., a person using the device and attending to the patient, to deliver a therapy to the patient based upon analysis of the physiological conditions of the patient.
When the heart of the patient is not perfusing, the cause of the non-perfusing rhythm could be VF, which may be responsive to defibrillation shock therapy. When shock therapy is to be applied, the medical personnel refrain from touching the patient, to avoid receiving an electric shock. When the heart of the patient is not perfusing for other reasons, however, the best course may be to reestablish perfusion by cardiopulmonary resuscitation (CPR) or other therapy that involves physical contact with the patient.